Camshaft adjusters are used in internal combustion engines to vary the timing of the combustion chamber valves in order to be able to vary the phase relation between a crankshaft and a camshaft in a defined angular range between a maximum advanced and a maximum retarded position. Adapting the timing to the current load and engine speed reduces consumption and emissions. For this purpose, camshaft adjusters are integrated into a drive train via which a torque is transmitted from the crankshaft to the camshaft. This drive train can be designed as a belt, chain or gear drive, for example.
In the case of a hydraulic camshaft adjuster, the output element and the input element form one or more pairs of opposing pressure chambers, which can be supplied with hydraulic fluid. The input element and the output element are arranged coaxially. By filling and emptying individual pressure chambers, a relative motion between the input element and the output element is produced. The spring acting for rotation between the input element and the output element urges the input element in a preferential direction relative to the output element. This preferential direction can be the same as or opposed to the direction of rotation.
One type of hydraulic camshaft adjuster is the vane cell adjuster. Vane cell adjusters have a stator, a rotor and a drive wheel with external teeth. The rotor is designed as an output element, generally in a manner which allows it to be connected for conjoint rotation to the camshaft. The input element comprises the stator and the drive wheel. The stator and the drive wheel are connected to one another for this purpose. The rotor is arranged coaxially with the stator and within the stator. The rotor and the stator, with their radially extending vanes, define oppositely acting oil chambers, which can be supplied with oil pressure and allow a relative rotation between the stator and the rotor. The vanes are either formed integrally with the rotor or the stator or are arranged as “inserted vanes” in grooves provided for that purpose in the rotor or the stator. Moreover, vane cell adjusters have various sealing covers. The stator and the sealing covers are secured to one another by a plurality of screw connections.
Another type of hydraulic camshaft adjuster is the axial piston adjuster. In this case, a sliding element is moved axially via oil pressure, producing a relative rotation between an input element and an output element by way of helical teeth.
Another type of camshaft adjuster is the electromechanical camshaft adjuster, which has a three-shaft mechanism (e.g. a planetary gear). In this case, one of the shafts forms the input element and a second shaft forms the output element. Via the third shaft, rotational energy can be fed to or removed from the system by a positioning device, e.g. an electric motor or a brake. A spring can be provided in addition, assisting or reversing the relative rotation between the input element and the output element.
DE 10 2007 020 524 A1 discloses a hydraulic camshaft adjuster of the vane-cell construction. For axial delimitation of the working chambers, this camshaft adjuster has two side covers or thrust washers, which are connected to the internal wheel and the camshaft by a screwed connection. For sealing, first and second sealing elements are provided and arranged between the respective thrust washer and the drive wheel, together with the integrally formed sleeve portion.
DE 198 30 100 A1 discloses a camshaft adjusting device having an impeller. The pressure chambers are sealed off by a sealing cage, which is also intended, inter alia, to seal off the pressure chambers with respect to the side walls of the drive wheel in a pressure tight manner.
DE 10 2008 019 745 A1 discloses a hydraulic camshaft adjuster, the housing of which is sealed off with respect to side covers arranged on the axial end faces thereof by second, O-ring-type sealing means, thus ensuring that no leakage occurs at the joint.